Polymer blends of ethylene-propylene copolymer or ethylene-propylene-diene terpolymer with poly .alpha.-olefins, particularly polyethylene and polypropylene, are known to the art (See U.S. Pat. Nos. 3,361,850; 3,176,052; 3,220,966; 3,751,521; 3,328,486; 3,793,283; 3,262,992; 3,036,987; and 3,536,653). At times, curing or crosslinking agents are added to alter the physical nature of the blend; i.e. to effect chemical changes in the blend (See U.S. Pat. Nos. 3,758,643; 3,806,558; 3,564,080; and 3,256,366). Polymer blends of poly .alpha.-olefins or of ethylene-propylene or ethylene-propylene-diene polymers with ethylene-vinyl acetate copolymers are also known (See U.S. Pat. Nos. 3,808,047; 3,422,055; 3,361,852; and 3,549,727). The use of curing or crosslinking agents in these blends is disclosed in U.S. Pat. Nos. 3,399,250; 3,789,085; and 3,784,668. None of the above cited art discloses a three-part blend of ethylene-propylene-diene polymer, polyethylene, and ethylene-vinyl acetate copolymer wherein the blend, without the use of curing or crosslinking agents, exhibits unexpectedly high tensile strength.